U.S. patent application number 12/685764 was filed with the patent office on 2010-07-22 for jet pump and reactor.
This patent application is currently assigned to Hitachi-GE Nuclear Energy, Ltd.. Invention is credited to Hisamichi Inoue, Naoyuki Ishida.
Application Number | 20100183113 12/685764 |
Document ID | / |
Family ID | 42336950 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100183113 |
Kind Code |
A1 |
Ishida; Naoyuki ; et
al. |
July 22, 2010 |
JET PUMP AND REACTOR
Abstract
A jet pump has a plurality of nozzles installed to a nozzle
base, a throat and a diffuser. A first nozzle straight-tube
portion, a first nozzle narrowing portion, a second nozzle
straight-tube portion, a second nozzle narrowing portion, and a
nozzle lower end portion formed in those nozzles are disposed in
this order from the nozzle base to a ejection outlet. A narrowing
angle of the second nozzle narrowing portion is larger than of the
first nozzle narrowing portion. The jet pump forms, in a lower end
portion of the throat, a flow passage narrowing portion having a
flow passage cross-sectional area that gradually diminishes. This
flow passage narrowing portion is inserted into an upper end
portion of the diffuser.
Inventors: |
Ishida; Naoyuki; (Hitachi,
JP) ; Inoue; Hisamichi; (Takahagi, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Assignee: |
Hitachi-GE Nuclear Energy,
Ltd.
|
Family ID: |
42336950 |
Appl. No.: |
12/685764 |
Filed: |
January 12, 2010 |
Current U.S.
Class: |
376/361 ;
417/198 |
Current CPC
Class: |
G21C 15/25 20130101;
Y02E 30/40 20130101; F04F 5/54 20130101; F04F 5/10 20130101; Y02E
30/30 20130101; F04F 5/462 20130101 |
Class at
Publication: |
376/361 ;
417/198 |
International
Class: |
G21C 15/00 20060101
G21C015/00; F04F 5/46 20060101 F04F005/46 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 22, 2009 |
JP |
2009-011479 |
Claims
1. A jet pump comprising: a nozzle apparatus for ejecting a driving
fluid; a throat for passing the driving fluid and a sucked suction
fluid; and a diffuser into which a downstream end portion of the
throat is inserted, wherein the nozzle apparatus has a nozzle base
member, and a plurality of nozzles installed to the nozzle base
member and forming a plurality of narrowing portions, in which a
fluid passage cross-sectional area of a driving fluid passage
formed in the nozzle is reduced; and, in the downstream end portion
of the throat inserted into the diffuser, a cross-sectional area of
a fluid passage formed in the throat diminishes toward the
downstream end of the throat.
2. A jet pump comprising: a nozzle apparatus having a header
portion disposing a first pipe member forming a suction fluid
passage for introducing a suction fluid, inside the head portion,
and including an annular passage, which surrounds the first pipe
member, for introducing a driving fluid, and a nozzle portion
installed to the header portion, surrounding the first pipe member,
and forming an ejection outlet, which is communicated with the
annular passage formed in the header portion, for ejecting the
driving fluid; a throat for passing the driving fluid ejected from
the ejection outlet and the sucked suction fluid; a diffuser into
which a downstream end portion of the throat is inserted; and a
second pipe member, one end of which is connected to the nozzle
apparatus, forming a driving fluid passage for introducing the
driving fluid to annular passage in the header portion, wherein the
first pipe member is disposed inside the driving fluid passage
formed in the second pipe member through the one end of the second
pipe member, and an opening for the suction fluid passage is formed
on an outer surface of the second pipe member and opened toward
outside of the second pipe member; the driving fluid passage is
formed in a way that the driving fluid flowing toward the one end
of the second pipe member hits the first pipe member diagonally in
the axial direction of the first pipe member; and, in the
downstream end portion of the throat inserted into the diffuser, a
cross-sectional area of a fluid passage formed in the throat
diminishes toward the downstream end of the throat.
3. The jet pump according to claim 2, wherein the second pipe
member is curved into an inverted U-shape.
4. The jet pump according to claim 2, wherein the jet pump has an
fluid-adjusting member installed in the second pipe member along
the central axis of the second pipe member.
5. The jet pump according to claim 4, wherein the fluid-adjusting
member is disposed upstream from the first pipe member.
6. A jet pump comprising: a nozzle apparatus for ejecting a driving
fluid; a throat for passing the driving fluid ejected from the
nozzle apparatus and a sucked suction fluid; and a diffuser into
which a downstream end portion of the throat is inserted, wherein
the nozzle apparatus has a first tubular member; a second tubular
member disposed in the first tubular member, apart from the first
tubular member; a fluid passage forming member disposed in the
first tubular member, and installed to an upper end portion of the
second tubular member; a plurality of passage members fixing both
ends to the first and the second tubular members and disposed in
the circumferential direction of the nozzle apparatus; and an
annular ejection outlet is formed between a lower portion of the
first tubular member and a lower portion of the second tubular
member; a suction passage formed in each of the passage members,
for introducing the suction fluid from the outside to the inside,
communicates with an inner region formed in the second tubular
member, an annular driving fluid passage for introducing the
driving fluid, across which each of the passage members is
disposed, is formed between the first tubular member, and the
second tubular member and the fluid passage forming member, and
communicated with the annular ejection outlet, an ejection
outlet-side portion of the driving fluid passage slopes inward
toward the lower end of the nozzle apparatus, and, in the
downstream end portion of the throat inserted into the diffuser, a
cross-sectional area of a fluid passage formed in the throat
diminishes toward the downstream end of the throat.
7. The jet pump according to claim 6, wherein the passage member
slopes toward a lower end of the nozzle apparatus as approaching
the inner region.
8. The jet pump according to claim 6, wherein a cross section of
the passage member, perpendicular to the axis of the passage member
is an oval shape.
9. The jet pump according to claim 8, wherein the passage member is
disposed in a way that the major axis of the oval shape follows the
axial direction of the nozzle apparatus.
10. The jet pump according to claim 6, wherein a surface of the
fluid passage forming member, facing the inner region is a curved
surface curved from an outlet of the suction passage to a lower end
of the fluid passage forming member.
11. The jet pump according to claim 10, wherein a cross-sectional
area of a portion where the curved surface of the fluid passage
forming member is formed decreases toward the lower end of the
fluid passage forming member.
12. The jet pump according to claim 6, wherein a cone member in
which a cross-sectional area decreases upward is disposed on an
upper end of the fluid passage forming member.
13. The jet pump according to claim 1, wherein, when water head of
a jet pump is H (Pa); a jet pump flow rate is Q (m.sup.3/s); and a
density of fluid flowing in the jet pump is .rho.(kg/m.sup.3), an
inner diameter D2 (m) of the downstream end of the throat is
(8.rho.(Q.sup.2/.pi.H).sup.0.25 or more, and smaller than an inner
diameter D1 (m) of the throat at where a cross-sectional area of
the fluid passage in the throat starts to diminish.
14. The jet pump according to claim 1, wherein a portion of the
throat, where the portion is inserted into the diffuser, is made
thick.
15. The jet pump according to claim 14, wherein a plurality of
grooves extending in the circumferential direction of the throat,
provided in the axial direction of the throat are formed on a
surface of the thick portion facing the diffuser.
16. The jet pump according to claim 1, wherein each of the nozzles
has a first nozzle straight-tube portion, a first nozzle narrowing
portion, a second nozzle straight-tube portion, a second nozzle
narrowing portion, and a nozzle lower end portion; an ejection
outlet is formed at a lower end of the nozzle lower end portion and
communicated with the driving fluid passage; and the first nozzle
straight-tube portion, the first nozzle narrowing portion, the
second nozzle straight-tube portion, the second nozzle narrowing
portion, and the nozzle lower end portion are disposed in this
order from the nozzle base member to the ejection outlet.
17. The jet pump according to claim 16, wherein a narrowing angle
of the second nozzle narrowing portion is larger than that of the
first nozzle narrowing portion.
18. A reactor having a reactor vessel and a plurality of jet pumps
installed in the reactor vessel, which jet pumps are for feeding
coolant to a core formed in the reactor vessel, wherein the jet
pumps comprises: a nozzle apparatus for ejecting a driving fluid; a
throat for passing the driving fluid and a sucked suction fluid;
and a diffuser into which a downstream end portion of the throat is
inserted, wherein the nozzle apparatus has a nozzle base member,
and a plurality of nozzles installed to the nozzle base member and
forming a plurality of narrowing portions, in which a fluid passage
cross-sectional area of a driving fluid passage formed in the
nozzle is reduced; and, in the downstream end portion of the throat
inserted into the diffuser, a cross-sectional area of a fluid
passage formed in the throat diminishes toward the downstream end
of the throat.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese Patent
application serial no. 2009-011479, filed on Jan. 22, 2009, the
content of which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to jet pump and reactor and,
in particular, to a jet pump and a reactor suitable for applying to
a boiling water reactor.
[0004] 2. Background Art
[0005] A conventional boiling water reactor (BWR) has a jet pump in
a reactor pressure vessel (hereinafter referred to as an RPV) to
which a recirculation pipe is connected. The jet pump has a nozzle,
a bell mouth, a throat, and a diffuser. Cooling water in a
downcomer, where the jet pump is disposed, formed in the RPV is
pressurized by operation of a recirculation pump, pumped through
the recirculation pipe as a driving flow, and ejected from the
nozzle into the throat. The nozzle increases the speed of the
driving flow. The cooling water around the nozzle in the downcomer
is sucked into the bell mouth as a suction flow due to the working
of the ejected driving flow, passes the throat, and flows into the
diffuser. The cooling water discharged from the diffuser is
supplied to a core through a lower plenum in the RPV (see, for
example, U.S. Pat. No. 3,625,820, Japanese Patent Laid-open No. Sho
59 (1984)-188100, Japanese Patent Laid-open No. Hei 7
(1995)-119700, and Japanese Patent Laid-open No. 2007-285165).
[0006] Jet pumps disclosed in Japanese Patent Laid-open No. Sho 59
(1984)-188100, Japanese Patent Laid-open No. Hei 7 (1995)-119700,
and Japanese Patent Laid-open No. 2007-285165 each have a plurality
of nozzles. When the total area of each ejection opening formed in
the plurality of nozzles remains constant, an increase in the
number of nozzles increases the contact area between driving flows
and suction flows, and thus mixing of the driving flows and the
suction flows is promoted. Consequently, a mixing loss is
decreased, increasing efficiency of the jet pump.
[0007] A jet pump installed in a reactor has a nozzle connected to
a raiser pipe that is installed in the RPV. In this jet pump, an
elbow pipe, the nozzle, a bell mouth and a throat are unified into
one body, which structure allows the elbow to the throat to be
removed for inspection and maintenance. A connection portion
between the throat and the diffuser has a joint structure in which
a lower end portion of the throat is inserted into an upper end
portion of the diffuser. This joint structure is a slip joint. The
slip joint, where the throat and the diffuser are connected, has a
structure which allows the upper end portion of the diffuser and
the lower end portion of the throat to slide up and down, so that
no stress is generated due to the difference between the thermal
expansions of the raiser pipe and the diffuser. For this reason, a
gap is formed between an inner surface of the diffuser's upper end
portion and an outer surface of the throat's lower end portion.
Part of the cooling water that flows into the diffuser from the
throat leaks out to the downcomer through the gap. This leakage
flow prevents a foreign object from being caught in the gap or
deposited on the surfaces. However, when the flow rate of the
leakage flow exceeds a limit, the jet pump may start to vibrate.
Thus, in order to suppress the vibration of the jet pump, the
leakage flow from the gap in the slip joint should be limited below
the limit.
[0008] Although it is not a jet pump, Japanese Examined Utility
Model Application Publication No. Sho 52 (1977)-5301 discloses a
fluid sealing joint used for pipes for introducing high-temperature
and high-pressure gas (or steam). In this fluid sealing joint, a
tubular inlet-side joint portion is inserted into a tubular
outlet-side joint portion; and an end portion of the inlet joint
portion has a narrowing portion whose flow passage cross-sectional
area decreases and an expanding portion whose cross-sectional area
increases toward the end. A communication hole is formed in the
place where the narrowing portion and the expanding portion are
connected, the flow passage cross-sectional area of which the place
is the smallest in the inlet-side joint portion. This communication
hole communicates with an annular space portion formed between the
inlet-side joint portion and the outlet-side joint portion. Static
pressure inside is reduced at the seam between the narrowing
portion and the expanding portion so that a fluid in the annular
space portion is sucked inside the narrowing portion through the
communication hole. This effectively prevents a fluid from leaking
out of the fluid sealing joint through a gap between the inlet-side
joint portion and the outlet-side joint portion.
[0009] Japanese Patent Laid-open No. Sho 59 (1984)-159489 discloses
a jet pump for suppressing vibration. In this jet pump, a lower end
portion of a throat, which is inserted into an upper end portion of
a diffuser, has a flow passage cross-sectional area that diminishes
toward the end.
[0010] Other than that, for the purpose of reducing the amount of
cooling water leaking from a slip joint of a jet pump, a way of
forming a labyrinth seal on an outer surface of a lower end portion
of a throat in the slip joint is known (see, for example, Japanese
Examined Patent Application Publication No. Sho 59
(1984)-48360).
[0011] A jet pump illustrated in FIG. 3 of Japanese Patent
Laid-open No. 2001-90700 has a venturi tube and a nozzle that
ejects a driving flow into the venturi tube a driving flow. This
nozzle has an inner cylinder and an outer cylinder that surrounds
the inner cylinder. A driving flow passage formed between the inner
cylinder and the outer cylinder is an annular passage whose
cross-sectional area gradually decreases towards the discharge side
of the driving flow. The driving flow supplied to the driving flow
passage is ejected from one end (a discharge opening) of the
driving flow passage into the venturi tube. Cleaning water around
the nozzle is sucked into the venturi tube due to the driving flow
ejected from the nozzle. To be more specific, this cleaning water
flows into the venturi tube through each of a first cooling water
suction passage formed between the nozzle and the venturi tube and
a second cooling water suction passage formed inside the inner
cylinder. From the nozzle, the annular driving flow is ejected.
Cross sections of the annular driving flow are similar to
continuous rings.
[0012] Japanese Patent Laid-open No. 2008-82752 discloses a jet
pump applicable to a BWR. This jet pump has a ring header for
supplying a driving flow surrounding a suction flow suction passage
formed in the center of the jet pump; and a nozzle portion
installed to a lower end of the ring header, surrounding the
suction flow suction passage, having a plurality of ejection
openings in an annular arrangement, where the ejection openings
eject a driving flow fed to the ring header.
PRIOR ART LITERATURES
Patent Literatures
[0013] Patent Literature 1: U.S. Pat. No. 3,625,820 [0014] Patent
Literature 2: Japanese Patent Laid-open No. Sho 59 (1984)-188100
[0015] Patent Literature 3: Japanese Patent Laid-open No. Hei 7
(1995)-119700 [0016] Patent Literature 4: Japanese Patent Laid-open
No. 2007-285165 [0017] Patent Literature 5: Japanese Examined
Utility Model Application Publication No. Sho 52 (1977)-5301 [0018]
Patent Literature 6: Japanese Patent Laid-open No. Sho 59
(1984)-159489 [0019] Patent Literature 7: Japanese Examined Patent
Application Publication No. Sho 59 (1984)-48360 [0020] Patent
Literature 8: Japanese Patent Laid-open No. 2001-90700 [0021]
Patent Literature 9: Japanese Patent Laid-open No. 2008-82752
SUMMARY OF THE INVENTION
Problem for Solving by the Invention
[0022] For the soundness of a jet pump, excessive vibration of the
jet pump is undesirable. Each slip joint disclosed in Japanese
Examined Utility Model Application Publication No. Sho 52
(1977)-5301 and Japanese Patent Laid-open No. Sho 59 (1984)-159489
can suppress a leakage flow from a slip joint and reduce vibration
caused by the leakage flow. However, each slip joint has a flow
passage cross-sectional area that changes, or decreases, where the
structure somewhat increases a pressure loss in the slip joint. For
this reason, when these slip joints are applied to a jet pump, the
efficiency of the jet pump is reduced for the increased amount of
pressure loss.
[0023] In Japanese Examined Patent Application Publication No. Sho
59 (1984)-48360, a labyrinth seal is provided to a slip joint. When
a labyrinth seal is fabricated on the outer surface of a throat,
its fabrication range is limited to the thickness of the throat and
the length of insertion. For this reason, when the fabrication
range is insufficient, a desired effect in leakage flow reduction
may not be achieved.
[0024] An object of the present invention is to provide a jet pump
and a reactor, which can suppress the vibration of the jet pump and
improve the efficiency of the jet pump.
Means for Solving the Problem
[0025] The present invention for achieving the above object is
characterized in that a nozzle apparatus has a nozzle base member,
and a plurality of nozzles installed to the nozzle base member and
forming a plurality of narrowing portions in which a fluid passage
cross-sectional area of a driving fluid passage formed in the
nozzle is reduced; and in a lower end portion of a throat inserted
into a diffuser, a cross-sectional area of a fluid passage formed
in the throat diminishes toward a downstream end of the throat.
[0026] Since, in the lower end portion of the throat inserted into
the diffuser, the cross-sectional area of the fluid passage formed
in the throat diminishes toward the downstream end of the throat,
the amount of a fluid leaking from a space between the throat and
the diffuser can be reduced and the vibration of the jet pump can
be suppressed.
[0027] Since the nozzle apparatus has the nozzle base member and
the plurality of nozzles installed to the nozzle base member and
forming the plurality of narrowing portions, in which the fluid
passage cross-sectional area of the driving flow passage is
reduced, inside itself, the efficiency of the jet pump can be
increased after compensating for a loss in jet pump efficiency
caused by the diminishment of the fluid passage cross-sectional
area in the throat.
[0028] The above object can also be achieved by a jet pump
comprising a nozzle apparatus having a header portion disposing a
first pipe member forming a suction fluid passage for introducing a
suction fluid, inside the head portion, and including an annular
passage, which surrounds the first pipe member, for introducing a
driving fluid, and a nozzle portion installed to the header
portion, surrounding the first pipe member, and forming an ejection
outlet, which is communicated with the annular passage formed in
the header portion, for ejecting the driving fluid; and a second
pipe member, one end of which is connected to the nozzle apparatus,
forming a driving fluid passage for introducing the driving fluid
to annular passage in the header portion,
[0029] wherein the first pipe member is disposed inside the driving
fluid passage formed in the second pipe member through the one end
of the second pipe member, and an opening for the suction flow
passage is formed on an outer surface of the second pipe member and
opened toward outside of the second pipe member;
[0030] the driving flow passage is formed in a way that the driving
fluid flowing toward the one end of the second pipe member hits the
first pipe member diagonally in the axial direction of the first
pipe member; and,
[0031] in the lower end portion of a throat inserted into a
diffuser, a cross-sectional area of a fluid passage formed in the
throat diminishes toward a downstream end of the throat.
[0032] Since, in the lower end portion of the throat inserted into
the diffuser, the cross-sectional area of the fluid passage formed
in the throat diminishes toward the downstream end of the throat,
the amount of a fluid leaking from a space between the throat and
the diffuser can be reduced and the vibration of the jet pump can
be suppressed.
[0033] Since the driving fluid passage formed inside the second
pipe member is formed so that the driving fluid flowing toward the
one end of the second pipe member hits the first pipe member
diagonally to the axial direction of the first pipe member,
pressure loss inside the driving fluid passage is decreased. Since
the speed of the driving fluid ejected from the annular ejection
outlet of the nozzle portion becomes faster, the flow rate of the
suction fluid sucked inside the jet pump body is increased. From
above, efficiency of the jet pump is improved. Part of this
increase in the jet pump efficiency can compensate for a decrease
in the jet pump efficiency caused by the diminishment of the flow
passage cross-sectional area in the throat.
[0034] The above object can also be achieved by a jet pump
comprising a nozzle apparatus having a first tubular member; a
second tubular member disposed in the first tubular member, apart
from the first tubular member; a fluid passage forming-member
disposed in the first tubular member, and installed to an upper end
portion of the second tubular member; a plurality of passage
members fixing both ends to the first and the second tubular
members and disposed in the circumferential direction of the nozzle
apparatus; and an annular ejection outlet is formed between a lower
portion of the first tubular member and a lower portion of the
second tubular member;
[0035] Wherein a suction passage formed in each of the passage
members, for introducing a suction fluid from the outside to the
inside, communicates with an inner region formed in the second
tubular member,
[0036] an annular driving fluid passage for introducing the driving
fluid, across which each of the passage members is disposed, is
formed between the first tubular member, and the second tubular
member and the flow passage forming member, and communicated with
the annular ejection outlet,
[0037] the ejection outlet-side portion of the driving fluid
passage slopes inward toward a lower end of the nozzle apparatus,
and,
[0038] in a lower end portion of a throat inserted into a diffuser,
a cross-sectional area of a fluid passage formed in the throat
diminishes toward a downstream end of the throat.
[0039] Since, in the lower end portion of the throat inserted into
the diffuser, the cross-sectional area of the fluid passage formed
in the throat diminishes toward the downstream end of the throat,
the amount of fluid leaking from a space between the throat and the
diffuser can be reduced and the vibration of the jet pump can be
suppressed.
[0040] Since the ejection outlet-side portion of the driving fluid
passage slopes inward toward the lower end of the nozzle apparatus,
degree of negative pressure in the inner region is increased,
increasing the flow rate of the suction fluid flowing into the
inner region through the suction passage. Furthermore, since the
ejection outlet-side portion of the driving fluid passage slopes
inward toward the lower end of the nozzle apparatus, the width of a
gap between the lower end of the outer circumference portion of the
nozzle apparatus and the upper end of a jet pump body is increased.
This increases the flow rate of a suction fluid flowing into the
jet pump body through the gap. From these increases in the flow
rates, the efficiency of the jet pump is further increased. Part of
this increase in the jet pump efficiency can compensate for a
decrease in jet pump efficiency caused by the diminishment of the
fluid passage cross-sectional area in the throat.
ADVANTAGEOUS EFFECT OF THE INVENTION
[0041] According to the present invention, the vibration of a jet
pump can be suppressed and the efficiency of the jet pump can be
improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] FIG. 1 is a perspective view showing a jet pump according to
embodiment 1 applied to a boiling water reactor, which is a
preferred embodiment of the present invention.
[0043] FIG. 2 is an enlarged longitudinal sectional view showing a
slip joint shown in FIG. 1.
[0044] FIG. 3 is a longitudinal sectional view showing a nozzle
apparatus shown in FIG. 1.
[0045] FIG. 4 is a longitudinal sectional view showing a boiling
water reactor to which the jet pump shown in FIG. 1 is applied.
[0046] FIG. 5 is a sectional view taken along V-V of FIG. 3.
[0047] FIG. 6 is a longitudinal sectional view showing a nozzle
shown in FIG. 3.
[0048] FIG. 7 is an explanatory drawing showing a change in
differential pressure between an inside of a jet pump and a
downcomer, from a throat inlet to a diffuser outlet of the jet
pump.
[0049] FIG. 8 is a characteristic drawing showing a relationship
between the M ratio and the efficiency of a jet pump in embodiment
1.
[0050] FIG. 9 is a longitudinal sectional view showing a nozzle
apparatus in a jet pump according to embodiment 2 applied to a
boiling water reactor, which is another embodiment of the present
invention.
[0051] FIG. 10 is a perspective view showing a nozzle apparatus
shown in FIG. 9.
[0052] FIG. 11 is a characteristic drawing showing a relationship
between the M ratio and the efficiency of a jet pump.
[0053] FIG. 12 is a longitudinal sectional view showing a nozzle
apparatus in a jet pump according to embodiment 3 applied to a
boiling water reactor, which is another embodiment of the present
invention.
[0054] FIG. 13 is a sectional view taken along XIII-XIII of FIG.
12.
[0055] FIG. 14 is a sectional view taken along XIV-XIV of FIG.
12.
[0056] FIG. 15 is a sectional view taken along XV-XV of FIG.
12.
[0057] FIG. 16 is a characteristic drawing showing a relationship
between the M ratio and the efficiency of a jet pump.
[0058] FIG. 17 is a longitudinal sectional view showing a slip
joint in a jet pump according to embodiment 5 applied to a boiling
water reactor, which is another embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] Various embodiments of the present invention are described
below.
Embodiment 1
[0060] A jet pump installed to a boiling water reactor, according
to an embodiment of the present invention is described below with
reference to FIGS. 1, 2, and 3. Before explaining a structure of
the jet pump of the present embodiment, an overall structure of a
boiling water reactor to which this jet pump is applied is
described below with reference to FIGS. 1 and 4.
[0061] The boiling water reactor (BWR) has a reactor pressure
vessel (reactor vessel) 1 and a core shroud 3 installed in the
reactor pressure vessel. Hereinafter, the reactor pressure vessel
is referred to as an RPV. A core 2 loaded with a plurality of fuel
assemblies (not shown) is disposed in the core shroud 3. A steam
separator 4 and a steam dryer 5 are disposed above the core 2 in
the RPV 1. A plurality of jet pumps 11 is disposed in an annular
downcomer 6 formed between the RPV 1 and the core shroud 3. A
recirculation system provided to the RPV 1 includes a recirculation
pipe 7 and a recirculation pump 8 installed to the recirculation
pipe 7. One end of the recirculation pipe 7 communicates with the
downcomer 6. Another end of the recirculation pipe 7 is connected
to a lower end of a raiser pipe 9 disposed in the downcomer 6. An
upper end of the raiser pipe 9 is connected to a branching pipe 60.
An elbow pipe (a curved pipe) 10 attached to the branching pipe 60
is connected to a nozzle apparatus 12 of the jet pump 11. A main
steam pipe 39 and a feed water pipe 28 are connected to the RPV 1.
The nozzle apparatus 12 is fixed to a bell mouth 21 using a
plurality of supporting plates 33, and makes up one body with the
bell mouth 21.
[0062] Cooling water (suction fluid, coolant), which is suction
flow existing in an upper portion of the RPV 1, is mixed with feed
water supplied from the feed water pipe 28 to the RPV 1, and
descends in the downcomer 6. This cooling water is sucked into the
recirculation pipe 7 by operation of the recirculation pump 8, and
pressurized by the recirculation pump 8. This pressurized cooling
water is called a driving flow (a driving fluid) 30 for descriptive
purposes. The driving flow 30 flows through the recirculation pipe
7, the raiser pipe 9, the branching pipe 60, and the elbow pipe 10,
and reaches the nozzle apparatus 12 of the jet pump 11 to be
ejected from the nozzle apparatus 12. The cooling water 32, which
is a suction flow around the nozzle apparatus 12 (see FIG. 3), is
sucked into a throat 22 from the bell mouth 21 due to the working
of a jet flow 31 of the driving flow 30 (see FIG. 3). The cooling
water 32 descends with the driving flow 30 in the throat 22, and
discharged from a lower end of a diffuser 25. The cooling water
discharged from the diffuser 25 (including the suction flow 32 and
the driving flow 30) is called cooling water 34 for descriptive
purposes. The cooling water 34 passes through a lower plenum 29 and
is supplied to the core 2. The cooling water 34 is heated while
passing the core 2 and becomes a two-phase flow including water and
steam. The steam separator 4 separates the gas-liquid two-phase
flow into steam and water. The steam dryer 5 removes further
moisture from the separated steam, and the steam from which the
moisture is removed is exhausted to the main steam pipe 39. This
steam is introduced to a steam turbine (not shown) and turns the
steam turbine. A power generator (not shown) coupled to the stream
turbine rotates to generate power. The steam exhausted from the
steam turbine becomes water through condensation in a condenser
(not shown). This condensed water is supplied into the RPV 1 as
feed water through the feed water pipe 28. The water separated by
the separator 4 and the dryer 5 descends and reaches the downcomer
6 as cooling water.
[0063] The jet pump 11 of the present embodiment, which has the
nozzle apparatus 12, the bell mouth 21, the throat 22, and the
diffuser 25 as its main components, can supply more cooling water
34 to the core with less driving flow 30 by sucking the cooling
water around the nozzle apparatus 12 in the downcomer 6. When the
kinetic energy of the driving flow 30 given by the recirculation
pump 8 effectively acts on the cooling water 32, more cooling water
32 is sucked into the jet pump 11 and the flow rate of the cooling
water 34 is increased more. The jet pump 11 reduces static pressure
in the throat 22 by ejecting the driving flow 30 (the jet flow 31)
at high speed from the nozzle apparatus 12 into the throat 22. This
makes the throat 22 suck in the cooling water 32, and allows the
necessary core flow rate to be obtained with a small amount of
power. The diffuser 25 has a flow passage cross-sectional area
which gradually increases toward the downstream direction within a
degree that prevents detachment of cooling water flow. This
diffuser 25 changes the kinetic energy of the cooling water into
pressure. In the diffuser 25, the pressure of the suction flow 32
is raised higher than the pressure at the position where the
suction flow is sucked into the bell mouth 21. A flow passage
cross-sectional area of the bell mouth 21 increases toward the
upstream direction.
[0064] The bell mouth 21, the throat 22, and the diffuser 25 are
disposed in this order from the upper position to the lower
position. A jet pump body comprises the bell mouth 21, the throat
22, and the diffuser 25. The nozzle apparatus 12 is disposed above
the bell mouth 21.
[0065] A structure of a slip joint 26 in the jet pump 11 of the
present embodiment is described with reference to FIG. 2. This slip
joint 26 has, in a lower end portion (a downstream end portion) of
the throat 22, a flow passage reduction portion 23 whose flow
passage cross-sectional area gradually diminishes toward a lower
end of the throat 22. An inner diameter D6 of a downstream end (the
lower end) of the flow passage reduction portion 23 is smaller than
an inner diameter D5 of an upstream end (an upper end) of the flow
passage reduction portion 23. Part of this flow passage reduction
portion 23 is inserted into an upper end portion (an upstream end
portion) of the diffuser 25. The flow passage reduction portion 23
has a thick-wall portion 24 on the outer surface. Formation of this
thick-wall portion 24 reduces the width of a gap 27 in the radial
direction of the throat 22, which gap is formed between the flow
passage reduction portion 23 and the diffuser 25.
[0066] A detailed structure of the nozzle apparatus 12 in the jet
pump 11 is described below with reference to FIGS. 3, 5, and 6. The
nozzle apparatus 12 has a nozzle base (a nozzle base member) 13 and
six nozzles 14. The nozzle base 13 of the nozzle apparatus 12 is
fixed to the bell mouth 21 by using the supporting plates 33 to
make up one body, and connected to the elbow pipe 10. The nozzle
apparatus 12 is disposed above the bell mouth 21. The nozzle base
13 has a protrusion 36 protruding downward, in the center of the
nozzle apparatus. The six nozzles 14 are fixed to the nozzle base
13 in an annular arrangement, disposed around the protrusion 36.
These nozzles 14 extend toward the bell mouth 21 from the nozzle
base 13.
[0067] A detailed structure of the six nozzles 14 provided to the
nozzle apparatus 12 is described with reference to FIG. 6. In the
nozzle 14, when the inner diameters, that is, the passage diameters
of a jet passage 35 formed inside the nozzle 14, are sequentially
defined as D1, D2, and D3 from the upstream end to the downstream
end of the nozzle 14, these inner diameters have a relationship
which is D1>D2>D3.
[0068] In the nozzle apparatus 12, the nozzle 14 has a nozzle
straight-tube portion 15, a nozzle narrowing portion 16, a nozzle
straight-tube portion 17, a nozzle narrowing portion 18, and a
nozzle lower end portion 19. The nozzle straight-tube portion 15
positioned in an uppermost position has a uniform inner diameter of
D1. In the nozzle narrowing portion 16, which is the first stage of
narrowing, connected to a downstream end of the nozzle
straight-tube portion 15, a flow passage cross-sectional area in
the narrowing portion 16 decreases toward a lower end of the nozzle
14, an inner diameter at an upper end is D1, the inner diameter at
a lower end is D2, and the length is L1. The nozzle straight-tube
portion 17 connected to the downstream end of the nozzle narrowing
portion 16 has a uniform inner diameter of D2. In the nozzle
narrowing portion 18, which is the second stage of narrowing,
connected to a downstream end of the nozzle straight-tube portion
17, a flow passage cross-sectional area in the narrowing portion 18
decreases toward the lower end of the nozzle 14, an inner diameter
at an upper end is D2, the inner diameter at a lower end is D3, and
the length is L2. The nozzle lower end portion 19 located in a
lowest position of the nozzle 14, connected to the lower end of the
nozzle narrowing portion 18 has an inner diameter of D3 and forms
an ejection outlet 20 in the end portion.
[0069] Unlike the nozzle in Japanese Patent Laid-open No. Sho 59
(1984)-188100, in which a nozzle narrowing portion is formed only
in one place in its end portion, the nozzle 14 narrows the jet
passage 35 in two places in the nozzle narrowing portions 16 and
18. A narrowing angle .theta.1 of the nozzle narrowing portion 16
and a narrowing angle .theta.2 of the nozzle narrowing portion 18
can be calculated by the following Equation (1) and Equation (2)
respectively.
.theta.1=tan.sup.-1((D1-D2)/2/L1) (1)
.theta.2=tan.sup.-1((D2-D3)/2/L2) (2)
[0070] The narrowing angle .theta.2 of the nozzle narrowing portion
18 near the ejection outlet 20 is larger than the narrowing angle
.theta.1 of the nozzle narrowing portion 16 (.theta.2>.theta.1).
The nozzle straight-tube portion 15 having a larger flow passage
cross-sectional area is disposed upstream from the nozzle narrowing
portion 16, and the nozzle straight-tube portion 17 having a
smaller flow passage cross-sectional area is disposed downstream
from the nozzle narrowing portion 16 respectively.
[0071] The nozzle lower end portion 19, which is a straight tube
having an inner diameter of D3 and the ejection outlet 20 in its
end, is preferably disposed at an outlet portion of the nozzle 14,
that is, the lower end portion of the nozzle 14. However, in order
to improve the flow speed of the jet flow 31 ejected from the
ejection outlet 20, a nozzle narrowing portion having a flow
passage cross-sectional area which gradually decreases toward the
downstream end may be used in place of the nozzle lower end portion
19 being the straight-tube.
[0072] When the nozzle narrowing portion having a flow passage
cross-sectional area which gradually decreases toward the
downstream end is used as the nozzle lower end portion 19, it is
preferable to reduce the narrowing angle .theta. of the nozzle
narrowing portion 18 of this nozzle to approximately less than 2
degrees in order to keep the spreading of the jet flow 31 from the
ejection outlet 20 of the nozzle lower end portion 19, within a
desirable range.
[0073] The driving flow 30 discharged from the recirculation pump 8
during the operation of the boiling water reactor is introduced
through the raiser pipe 9 and the elbow pipe 10 and supplied into
the nozzle base 13 of the nozzle apparatus 12. This driving flow 30
is introduced to the jet passage 35 of each nozzle 14. A flow
passage cross-sectional area of the jet passage 35 varies according
to the inner diameters of the nozzle straight-tube portion 15, the
nozzle narrowing portion 16, the nozzle straight-tube portion 17,
the nozzle narrowing portion 18, and the nozzle lower end portion
19 disposed from the upper position to the lower position. The
driving flow 30 flowing into the jet passage 35 flows through the
nozzle straight-tube portion 15, the nozzle narrowing portion 16,
the nozzle straight-tube portion 17, and the nozzle narrowing
portion 18, and reaches the nozzle lower end portion 19. The
driving flow 30 descends in the jet passage 35 gradually gains
speed in the nozzle narrowing portion 16, and gains speed even
faster in the nozzle narrowing portion 18 than in the nozzle
narrowing portion 16. The accelerated driving flow 30 is ejected
from the ejection outlet 20 into the throat 22.
[0074] In the nozzle narrowing portion 18, a velocity component
toward the central axis of the nozzle 14 is given to the driving
flow 30. However, since a fluid has a characteristic to flow along
a wall surface, the jet flow 31 ejected from the ejection outlet 20
formed at the lower end of the nozzle lower end portion 19 has a
diameter of D3. Since the larger the narrowing angle .theta.2 of
the nozzle narrowing portion 18, the more the momentum flows toward
the central axis of the nozzle, the spreading of the jet flow 31
ejected from the ejection outlet 20 can be suppressed. As a
consequence, and the diameter D4 of the jet flow 31, which is a
distance L3 away from the ejection outlet 20 in the downstream
direction, can be small within a desirable range. The diameter D4
of the jet flow 31 is a width of the jet flow 31. The smaller the
diameter D4 of the jet flow 31, the faster the speed of this jet
flow.
[0075] When the jet flow 31 is ejected from the nozzle 14 into the
throat 22 while the spreading of the jet flow 31 is suppressed and
its speed maintained, the static pressure inside the throat 22 is
reduced, making more suction flow 32 around the nozzle apparatus 12
in the downcomer 6 to be sucked into the bell mouth 21.
[0076] Assume that no nozzle lower end portion 19 is disposed
downstream from the nozzle narrowing portion 18. In this case, a
diameter of the jet flow 31 keeps decreasing even after being
ejected because of the momentum of the driving flow 30 toward the
central axis of the nozzle 14, given in the nozzle narrowing
portion 18. That is, since no straight-tube portion of the nozzle
lower end portion 19 is provided, the jet flow 31 ejected from the
ejection outlet 20 formed in the lower end of the nozzle 14 is
affected by the nozzle narrowing portion 18. This makes the
diameter D4 of the jet flow 31 at the distance L3 away from the
ejection outlet 20 in the downstream direction, smaller than the
inner diameter D3 of the ejection outlet 20. Thus, the jet speed is
raised and the acceleration loss is increased, reducing the flow
rate of the driving flow 30.
[0077] For this reason, the nozzle lower end portion 19 being the
straight-tube portion is installed in the downstream side of the
nozzle narrowing portion 18 to keep the diameter of the jet flow 31
ejected from the ejection outlet 20 to be no smaller than the inner
diameter D3 of the nozzle lower end portion 19 being the
straight-tube portion. The installation of the nozzle lower end
portion 19 prevents the reduction in the flow rate of the driving
flow 30 caused by the increase in the acceleration loss.
[0078] In addition, the nozzle narrowing portions are provided to
the nozzle 14 in two or more locations to reduce the 25, pressure
loss in the nozzle 14 as well as to widen the flow passage for the
suction flow 32, formed between the nozzles 14.
[0079] Next, the following case is considered where the inner
diameter of the ejection outlet 20 is fixed to D3, the nozzle
narrowing portion 16 is made straight, each inner diameter of the
nozzle straight-tube portion 15 and the nozzle narrowing portion
16, which is now a straight tube, is set to D2, and a nozzle
narrowing portion formed in the nozzle 14 is only in one place in
the nozzle narrowing portion 18. When the length L2 of the nozzle
narrowing portion 18 is unchanged, the flow passage cross-sectional
areas of the nozzle straight-tube portion 15 and the nozzle
narrowing portion 16, which is now straight, become smaller,
increasing the flow speed of the driving flow 30 flowing inside.
Consequently, a loss in friction is increased and the flow rate of
the driving flow 30 is reduced. When the length L2 of the nozzle
narrowing portion 18 is extended to enlarge the flow passage
cross-sectional area of the nozzle narrowing portion 18 in the
upstream side, the outer diameter of the nozzle 14 becomes larger
and a flow passage cross-sectional area of the suction flow 32
formed among the plurality of nozzles 14 becomes smaller, reducing
the suction amount of the suction flow 32 into the bell mouth
21.
[0080] Therefore, in the present embodiment that two or more nozzle
narrowing portions are provided to the nozzle 14, a flow passage
cross-sectional area of the jet passage 35 in the nozzle 14 becomes
smaller toward the ejection outlet 20, and the flow speed of the
driving flow 30 flowing in the jet passage 35 is increased. Because
of this, the area where the loss in friction is increased in the
jet passage 35 can be reduced. In addition, since the outer
diameter of the nozzle 14 can be made smaller below the nozzle
narrowing portion 16, a space 37 (see FIG. 5) formed among the
nozzles 14 can be larger, and the flow rate of the suction flow 32
sucked into a region 38 (see FIG. 3) inside the six nozzles 14 can
be increased. As a result, the flow rate of the suction flow 32
sucked into the throat 21 is increased.
[0081] As described above, the driving flow 30 flowing into the jet
passage 35 is accelerated in the jet passage 35 by the nozzle
narrowing portions 16 and 18, and ejected from the ejection outlet
20 into the throat 22 as the jet flow 31. In the present
embodiment, the spreading of the jet flow 31 is kept small so that
the speed of the jet flow 31 reached inside the throat 22 is
higher, reducing the static pressure inside the throat 22. As a
result, more suction flow 32 can be sucked into the throat 22.
[0082] The present embodiment provides the nozzle 14 having two
nozzle narrowing portions 16 and 18 so that the flow rate of the
suction flow 32 sucked into the throat 22 can be increased, by the
above-described working of the nozzle 14, more than the
conventional jet pump disclosed in Japanese Patent Laid-open No.
Sho 59 (1984)-188100 which provides five nozzles, each having one
stage of a narrowing portion and a straight-tube portion. For this
reason, the flow rate of the cooling water 34 discharged from the
jet pump 11 is increased, and the efficiency of the jet pump 11 in
a high-M ratio range can be improved more than that of the
conventional jet pump.
[0083] An example of a change in the differential pressure between
the inside of the jet pump and the downcomer 6 in the axial
direction of the jet pump from the inlet of the throat to the
outlet of the diffuser is shown in FIG. 7. In FIG. 7, the broken
line shows a characteristic of a conventional jet pump having five
nozzles, which has been used in a boiling water reactor of a
million kW class. As shown here, the high-speed ejection of a
driving flow from the nozzle causes the static pressure in the
throat to be lower than the static pressure in the downcomer 6,
making the differential pressure between the inside and the outside
of the throat inlet portion negative. The differential pressure
between the inside of the jet pump and the downcomer 6 becomes
positive at a position of a slip joint, and a magnitude of this
positive pressure increases toward the diffuser outlet. In the
conventional jet pump, in the lower portion of the throat, the
static pressure in the throat is recovered by gradually increasing
the flow passage cross-sectional area toward the downstream end of
the throat. When the static pressure in the jet pump at the
position of the slip joint is larger than the static pressure in
the downcomer 6 at the same location, cooling water starts to leak
from the inside of the jet pump to the downcomer 6 through a gap in
the slip joint. When the amount of this leakage flow is excessive,
the jet pump may vibrate undesirably.
[0084] In the slip joint 26 of the jet pump 11 of the present
embodiment, as described above, the flow passage reduction portion
23 formed in the downstream end portion of the throat 22 is
inserted into the upstream end portion of the diffuser 25 so that
the flow speed of the cooling water flowing into the diffuser 25
from the flow passage reduction portion 23 is increased, reducing
the static pressure in the diffuser 25 in the vicinity of the
downstream end of the flow passage reduction portion 23.
[0085] This reduces the difference between the static pressure in
the jet pump 11, that is, the static pressure in the diffuser 25,
and the static pressure in the downcomer 6 at the installation
position of the slip joint 26. By using the method that can reduce
the difference between these static pressures, the amount of the
cooling water leaking to the downcomer 6 through the gap 27 in the
slip joint 26 can be reduced more surely than by using the method
such as in Japanese Examined Patent Application Publication Sho 59
(1984)-48360 which provides a labyrinth seal whose effect in
reducing the leakage flow is limited by an available range of
fabrication. Consequently, in the present embodiment, the vibration
of the jet pump 11 can be controlled.
[0086] The solid line in FIG. 7 shows a change in the differential
pressure between the inside of the jet pump 11 and the downcomer 6,
when the jet pump 11 in the present embodiment is used, in which
jet pump 11, the inner diameter of the downstream end of the throat
22 is made, by forming the flow passage reduction portion 23, 6%
smaller than the inner diameter of the downstream end of the throat
in the conventional jet pump having no flow passage reduction
portion 23. In the present embodiment, the static pressure starts
to decrease at the starting point of the flow passage reduction
portion 23, and the differential pressure between the inside of the
jet pump 11 and the downcomer 6 at the position of the slip joint
26 drops to about a half of that in the conventional example shown
in the broken line. After that, the velocity energy of the cooling
water is changed to pressure as the flow passage cross-sectional
area in the diffuser 25 is increased, recovering the pressure in
the diffuser 25. The drop in the differential pressure between the
inside of the jet pump 11 and the downcomer 6 at the position of
the slip joint 26 reduces the vibration of the jet pump 11 as
described above.
[0087] However, the present embodiment increases a pressure loss
more than the conventional jet pump because of the formation of the
flow passage reduction portion 23. As a result, in the present
embodiment shown in the solid line, the pressure at the outlet of
the diffuser 25 is lower than that in the conventional example
shown in the broken line (see FIG. 7). This reduces the flow rate
of the cooling water 34 supplied to the core 2 from the jet pump.
In other words, the formation of the flow passage reduction portion
23 reduces the efficiency of the jet pump.
[0088] The jet pump 11 of the present embodiment, as described
above, tries to improve the efficiency of the jet pump by
installing the nozzle apparatus 12 having six nozzles 14 with two
stages of nozzle narrowing portions. In the jet pump 11, the
reduction in the jet pump efficiency due to the formation of the
flow passage reduction portion 23 can be compensated by part of the
improvement in the jet pump efficiency achieved by using the nozzle
apparatus 12. Thus, the jet pump 11 can prevent the vibration of
the jet pump and at the same time, can improve the efficiency of
the jet pump more than the conventional jet pump.
[0089] The improvement in the efficiency of the jet pump of the
present embodiment is explained in detail with reference to FIG. 8.
In FIG. 8, the broken line shows the efficiency of the conventional
jet pump (the conventional jet pump having the characteristic shown
by the broken line in FIG. 7) having a nozzle apparatus with five
nozzles. In this conventional jet pump, a flow passage
cross-sectional area of the downstream end of the throat is set to
a conventional ratio of 100%, and each nozzle has one stage of
narrowing portion as in the jet pump disclosed in Japanese Patent
Laid-open No. Sho 59 (1984)-188100. The alternate long and short
dash line in FIG. 8 shows the efficiency of a jet pump of a
comparative example, in which the throat in the conventional jet
pump having the characteristic shown in the broken line is replaced
with a throat having the same flow passage reduction portion 23 as
in the present embodiment, in the lower end portion. In the jet
pump of the comparative example, a flow passage cross-sectional
area of the downstream end of the flow passage reduction portion 23
is 90% of a flow passage cross-sectional area of the corresponding
position in the conventional jet pump having the characteristic
shown in the broken line. For this jet pump, since the pressure
loss is increased by forming the flow passage reduction portion 23
in the throat, the efficiency of the jet pump is lower than that
shown in the broken line. The efficiency of the conventional jet
pump having the flow passage reduction portion in the throat is
reduced by approximately 0.7%. In FIG. 8, the solid line shows the
jet pump efficiency of the jet pump 11 of the present embodiment.
In the jet pump 11, a flow passage cross-sectional area of the
downstream end of the flow passage reduction portion 23 in the
throat 22 is also 90%. In the jet pump 11, the reduction in the jet
pump efficiency caused by the formation of the flow passage
reduction portion 23 in the throat 22 is covered by the increase in
the jet pump efficiency achieved by using the nozzle apparatus 12.
As a result, the jet pump efficiency is improved more than the jet
pump efficiency of the jet pump of the conventional example shown
in the broken line. In the present embodiment, the efficiency of
the jet pump is improved by approximately 3% more at the peak
compared to that of the conventional jet pump without the flow
passage reduction portion in the throat.
[0090] In the jet pump 11 of the present embodiment, the number of
the nozzles 14 is increased to six. By using two stages of the
nozzle narrowing portions 16 and 18, the spreading of the jet flow
31 ejected from the ejection outlet 20 can be kept small,
suppressing the reduction in the speed of the jet flow 31 that has
reached the inlet of the throat 22 as well as the decrease in the
suction area for the suction flow 32 in the throat 22. This allows
more suction flow 32 to be sucked into the throat 22 at the same
ejecting speed of the jet flow 31. In addition, in the present
embodiment, the total flow passage cross-sectional area of the
ejection outlets 20 of the six nozzles 14 is made the same as that
of the conventional five nozzles, while making the total length of
wetted perimeter of the six nozzles 14 approximately 9% more than
that of the conventional five nozzles. This increases the contact
area between the suction flow 32 and the jet flow 31 of the driving
flow 30 ejected from the ejection outlet 20, making both fluids to
be mixed faster, which reduces a loss during the mixing.
[0091] The jet pump 11 of the present embodiment can improve the
jet pump efficiency compared to the conventional jet pump disclosed
in Japanese Patent Laid-open No. Sho 59 (1984)-188100 which
provides five nozzles, each having one stage of a narrowing portion
and a straight-tube portion.
[0092] In the present embodiment, since the narrowing angle
.theta.2 of the nozzle narrowing portion 18 is made larger than the
narrowing angle .theta.1 of the nozzle narrowing portion 16, the
spread of the jet flow 31 is suppressed and which prevents the
reduction in the speed of the driving flow 30 at the inlet of the
throat 22 is also suppressed. At the same time, since the nozzle
lower end portion 19 forming the ejection outlet 20 is provided, it
can be prevented to accelerate excessively the driving flow 30 by
the narrowing portion and to increase the pressure loss in the
nozzle 14.
[0093] Since the speed of the driving flow 30 in the throat 22 is
not much slower than the speed at the ejection outlet 20, the
static pressure in the throat 22 is reduced and the suction amount
of the suction flow 32 into the throat 22 is increased.
Consequently, the M ratio and the efficiency of the jet pump can be
improved.
[0094] In a boiling water reactor, a rotational speed of the
recirculation pump 8 is controlled to adjust a flow rate of cooling
water supplied to the core 2 (a core flow rate).
[0095] The improvement in the M ratio and the jet pump efficiency
allows the core flow rate to be increased using less power from the
recirculation pump. Thus, power consumption for driving the
recirculation pump 8 can be reduced. In addition, when a power
upgrade of a reactor in the U.S. is to be implemented, the core
flow rate can be further increased without increasing the capacity
of the recirculation pump 8 by employing, for the existing reactor,
the jet pump 11 of the present embodiment which can increase the M
ratio and the jet pump efficiency. For this reason, the power
upgrade of the boiling water reactor can be easily achieved.
Embodiment 2
[0096] A jet pump according to embodiment 2, which is another
embodiment of the present invention, is described below.
[0097] The jet pump is also applied to a boiling water reactor. A
jet pump 11A of the present embodiment has a structure in which the
nozzle apparatus 12 in the jet pump 11 of the embodiment 1 is
replaced with a nozzle apparatus 12A. Other components of the jet
pump 11A are the same as the jet pump 11. The nozzle apparatus 12A
is explained below with reference to FIGS. 9 and 10.
[0098] In the jet pump 11A, minimizing the loss in pressure and
making the most of the suction power induced by a driving flow are
both important to increase the M ratio and the N ratio and to raise
the efficiency of the jet pump.
[0099] The jet pump 11A of the present embodiment has an inner
cooling water suction passage 50 in and through the nozzle
apparatus 12A in the axial direction. The inner cooling water
suction passage 50 has, in its upper end, an opening 51 which
communicates with the downcomer 6. Furthermore, in the jet pump
11A, the inner cooling water suction passage 50 extends upward
inside the elbow pipe 10, and the opening 51 is formed on the outer
surface of the elbow pipe 10 at a position lower than a top point
TP of the elbow pipe 10.
[0100] The nozzle apparatus 12A, as shown in FIG. 9, has a nozzle
portion 40 and a nozzle header portion 46. The nozzle header
portion 46 has an outer cylinder member 47 and an inner cylinder
member 48 disposed inside the outer cylinder member 47. An annular
header portion 49 is formed between the outer cylinder member 47
and the inner cylinder member 48, both of which are disposed in a
concentric manner. The nozzle portion 40 is disposed below the
nozzle header portion 46, and fixed to a lower end portion of the
nozzle header portion 46.
[0101] The nozzle portion 40 has an outer cylinder member 41, an
inner cylinder member 42, an outer funnel member 43, and an inner
funnel member 44. The outer cylinder member 41 surrounds the inner
cylinder member 42, and the outer cylinder member 41 and the inner
cylinder member 42 are concentrically disposed. The outer funnel
member 43 surrounds the inner funnel member 44, and the outer
funnel member 43 and the inner funnel member 44 are concentrically
disposed. The outer funnel member 43 and the inner funnel member 44
each have a cross-sectional area that decreases downward. The outer
funnel member 43 is fixed to an upper end of the outer cylinder
member 41, and the inner funnel member 44 is fixed to an upper end
of the inner cylinder member 42. The outer funnel member 43 is
attached to a lower end of the outer cylinder member 47. The inner
funnel member 44 is attached to a lower end of the inner cylinder
member 48. An annular ejection outlet 20A is formed between the
outer cylinder member 41 and the inner cylinder member 42.
[0102] An outlet end 53 of the elbow pipe 10 is fixed to the nozzle
header portion 46, that is, an upper end of the outer cylinder
member 47. An inlet end 52 of the elbow pipe 10 is placed on an
upper end of the branching pipe 60. The elbow pipe 10 and the
branching pipe 60 are detachably coupled with a fixture. The center
of the outlet end 53 of the elbow pipe 10 matches an axis of the
nozzle header portion 46, that is, the outer cylinder member 47.
The nozzle portion 40, the nozzle header portion 46, and the elbow
pipe 10 are joined into one body by welding.
[0103] The inner cylinder member 48 is inserted into the elbow pipe
10 through the outlet end 53, and extends upward. The opening 51
located in the upper end portion of the inner cylinder member 48 is
formed on the outer surface of the elbow pipe 10 and communicates
with the downcomer 6. The upper end of the inner cylinder member 48
is welded to the elbow pipe 10. A joint (a fixed position) 57 which
is the highest position in a joint portion (a fixed portion)
between the inner cylinder member 48 and the elbow pipe 10 is
disposed lower than the top point TP which is the highest position
on the outer surface of the elbow pipe 10.
[0104] A flow-adjusting plate (a flow-adjusting member) 54 having
the same curvature as the elbow pipe 10 is installed inside the
elbow pipe 10, and disposed from the inlet end 52 of the elbow pipe
10 to the inner cylinder member 48 along the axis of the elbow pipe
10. The flow-adjusting plate 54 is disposed upstream from the inner
cylinder member 48. An upper passage 55 and a lower passage 56 that
are separated into the top and the bottom, are formed in the elbow
pipe 10 by the installation of the flow-adjusting plate 54. Since
the joint 57 is located lower than the top point TP, the upper flow
passage 55 and the lower passage 56 in the elbow pipe 10 extending
toward the outlet end 53 are formed diagonally to the axis of the
inner cylinder member 48. In other words, the upper passage 55 and
the lower passage 56 are formed so that the driving flows in the
flow passages flowing toward the outlet end 53, hitting the inner
cylinder member 48 diagonally in relation to the axial direction of
the inner cylinder member 48.
[0105] The inner cooling water suction passage 50 communicating
with the downcomer 6 through the opening 51 is formed inside the
joined inner cylinder member 48, inner funnel member 44, and inner
cylinder member 42. The joined inner cylinder member 48, inner
funnel member 44, and inner cylinder member 42 are a first pipe
member. The inner cooling water suction passage 50 has a flow
passage cross-sectional area which gradually decreases downward in
the inner funnel member 44, and its lower end opens toward the bell
mouth 21. An annular passage 45 formed between the outer funnel
member 43 and the inner funnel member 44, communicating with the
annular header portion (an annular passage) 49 and the annular
ejection outlet 20A, has a flow passage cross-sectional area which
gradually decreases downward.
[0106] The driving flow pressurized by the recirculation pump 8
during the operation of the boiling water reactor reaches the
raiser pipe 9 and is introduced into the annular header portion 49
through the elbow pipe 10. The flow-adjusting plate 54 disposed in
the elbow pipe 10 reduces the pressure loss in the elbow pipe 10.
Part of the driving flow flowing in each of the upper passage 55
and the lower passage 56 in the elbow pipe 10 toward the outlet end
53 hits the outer surface of the inner cylinder member 48
diagonally in relation to the axial direction of the first pipe
member (the inner cylinder member 48 in particular). The driving
flow introduced into the annular header portion 49 flows through
the annular passage 45 and is ejected at high speed into the bell
mouth 21 from the annular ejection outlet 20A. The cross-sectional
area of the jet flow of the driving flow ejected from the annular
ejection outlet 20A is annular. The high-speed supplying of the jet
flow of the driving flow into the throat 22 reduces the static
pressure in the throat 22, making the cooling water around the
nozzle apparatus 12A in the downcomer 6 to be sucked into the bell
mouth 21.
[0107] There are two patterns for the cooling water being the
suction flow around the nozzle apparatus 12A to be sucked into the
bell mouth 21 due to the reduction in the static pressure in the
throat 22. The first pattern is that the cooling water above the
elbow pipe 10 flows into the inner cooling water suction passage 50
from the opening 51, and reaches the bell mouth 21 through the
inner cooling water suction passage 50. In this pattern, the
cooling water sucked through the inner cooling water suction
passage 50 flows into the inside of the annular jet flow ejected
from the annular ejection outlet 20A. The second pattern is that
the cooling water in the downcomer 6 passes through an outer
cooling water suction passage 58 formed between the nozzle portion
40 and the bell mouth 21, and reaches the bell mouth 21 at the
outside of the annular jet flow. The driving flow ejected from the
annular ejection outlet 20A and the cooling water (the suction
flow) sucked into the bell mouth 21 by the working of the driving
flow are mixed in the throat 22 by exchanging their momentum, and
introduced to the diffuser 25 located below the throat 22. The
cooling water 34 discharged from the diffuser 25 is introduced to
the core 2 through the lower plenum 29.
[0108] In the present embodiment, since the joint portion 57 is
positioned lower than the top point TP, the upper passage 55 and
the lower passage 565 in the elbow pipe 10 are formed toward the
outlet end 53, diagonally to the inner cylinder member 48 forming
the inner cooling water suction passage 50 in the axial direction
of the inner cylinder member 48. For this reason, the pressure loss
in the elbow pipe 10 where the inner cylinder member 48 exists is
reduced, and the flow speed of the cooling water ejected from the
annular ejection outlet 20A is increased. The reduction amount of
the static pressure in the throat 22 is increased, increasing the
flow rate of the cooling water sucked into the bell mouth 21
through the inner cooling water suction passage 50 and the outer
cooling water suction passage 58. This increase in the flow rate of
the cooling water improves the efficiency of the jet pump 11A.
[0109] This improvement in the efficiency of the jet pump 11A is
explained. FIG. 11 shows a relationship between the M ratio and the
jet pump efficiency of a jet pump having the nozzle apparatus 12A
with no flow passage reduction portion in the throat, and that of a
jet pump of a comparative example. In FIG. 11, the solid line shows
a characteristic of the jet pump having the nozzle apparatus 12A
with no flow passage reduction portion in the throat, and the
broken line shows a characteristic of the comparative jet pump. The
jet pump of the comparative example uses the nozzle apparatus shown
in FIG. 3 of Japanese Patent Laid-open No. 2001-90700 as a nozzle
for the jet pump in a SWR, disclosed in U.S. Pat. No. 3,625,820.
While in the comparative example, a pressurized driving flow hits
an inner cylinder of the nozzle apparatus at a right angle, in the
jet pump having the nozzle apparatus 12A with no flow passage
reduction portion in the throat, a driving flow flowing through a
cooling water passage in the elbow pipe 10 hits the inner cylinder
member 48 diagonally as described above. Because of such a
difference in the driving flows, the pressure loss of the jet pump
having the nozzle apparatus 12A with no flow passage reduction
portion in the throat is less than that of the comparative example.
Consequently, in the jet pump having the nozzle apparatus 12A with
no flow passage reduction portion in the throat, the efficiency of
the jet pump is increased by more than that of the comparative
example for the amount of the reduced pressure loss in the
nozzle.
[0110] Since the jet pump 11A of the present embodiment has the
flow passage reduction portion 23 in the lower end portion of the
throat 22 in the same manner as the jet pump 11 of the embodiment
1, in the jet pump 11A, the flow passage reduction portion 23
causes the efficiency of the jet pump to decrease. However, this
reduction in the efficiency can be compensated for by part of the
increase in the efficiency achieved by the nozzle apparatus
12A.
[0111] From the contribution of the remaining increase in the
efficiency achieved by the nozzle apparatus 12A, the jet pump 11A,
thus, can improve the efficiency of the jet pump more than that of
the comparative example.
[0112] In the present embodiment, a leakage flow from the gap 27 in
the slip joint 26 can be reduced because the flow passage reduction
portion 23 is formed in the lower end portion of the throat 22. For
this reason, the vibration of the jet pump 11A can be
suppressed.
[0113] In the present embodiment, since the flow-adjusting plate 54
is installed in the elbow pipe 10, the pressure loss in the elbow
pipe 10 can be further reduced. The reduction in the pressure loss
further increases the efficiency of the jet pump 11A. Since the
flow-adjusting plate 54 is disposed upstream from the inner
cylinder member 48, separation of the flow and uneven distribution
of speed in the elbow pipe 10 are improved, and the pressure loss
in the elbow pipe 10 is reduced.
[0114] Since the cooling water passages (the upper passage 55 and
the lower passage 56) formed in the elbow pipe 10 are diagonal to
the inner cylinder member 48 as described above, the driving flow
flowing in the cooling water passages hits the outer surface of the
inner cylinder member 48 diagonally to the axial direction of the
inner cylinder member 48. This causes the stress generated at the
contact portion between the inner cylinder member 48 and the elbow
pipe 10 to be small. Thus, when the nozzle apparatus 12A is applied
to a current BWR, it is not necessary to reinforce the joint
portion by making the member particularly thick, or to modify the
raiser pipe 9 and the fixture.
[0115] In the present embodiment, Since the inner cooling water
suction passage 50 is formed in the nozzle apparatus 12A, the
effect of the pressure reduction in the area inside the ejected
annular jet flow can be effectively used. This generates the flow
of the cooling water reaching into the bell mouth 21 through the
inner cooling water suction passage 50. Thus, since cooling water
can flow into the bell mouth 21 through each of the inner cooling
water suction passage 50 and the outer cooling water suction
passage 58, the flow rate of the cooling water flowing into the
bell mouth 21 is increased.
[0116] The inner cooling water suction passage 50 is disposed in
the axial direction of the RPV 1, and the opening 51 opens upward,
so that the flow power of the cooling water descending in the
downcomer 6, supplied to the inner cooling water suction passage
50, can be effectively utilized to increase the suction power of
the jet pump 11A. This increases the rate of the cooling water
sucked into the throat 22. In addition, since the nozzle portion 40
has the outer funnel member 43 whose outer diameter decreases
downward, the nozzle apparatus 12A has a structure that allows the
cooling water descending in the downcomer 6 to be easily sucked
into the bell mouth 21 through the outer cooling water suction
passage 58. This also increases the flow rate of the cooling water
flowing into the bell mouth 21, increasing the efficiency of the
jet pump 11A.
[0117] In the boiling water reactor installed with the jet pump
11A, the core flow rate can be further increased without increasing
the capacity of the recirculation pump 8 in the same manner as in
the embodiment 1. For this reason, a power upgrade of the boiling
water reactor can be easily achieved.
[0118] Furthermore, in the present embodiment, the inverted
U-shaped elbow pipe 10 is connected to the nozzle apparatus 12A so
that a single raiser pipe 9 disposed in the downcomer 6 can be
connected to two jet pumps 11A adjacent to the raiser pipe 9, with
the elbow pipes 10 each connected to the nozzle apparatus 12A of
each of the two jet pumps 11A. For this reason, a space between the
jet pumps 11A can be made equal to the corresponding space in the
existing boiling water reactor.
Embodiment 3
[0119] A jet pump according to embodiment 3, which is another
embodiment of the present invention, is described below. A jet pump
11B of the present embodiment has a structure in which the nozzle
apparatus 12 in the jet pump 11 in the embodiment 1 is replaced
with a nozzle apparatus 12B. Other components of the jet pump 11B
are the same as the jet pump 11. The nozzle apparatus 12B is
explained below with reference to FIG. 12.
[0120] The nozzle apparatus 12B, as shown in FIG. 12, has a nozzle
portion 61, a suction passage portion 65, and a nozzle holder 78.
The suction passage portion 65 is disposed above the nozzle portion
61, and installed on the upper end of the nozzle portion 61. The
nozzle holder 78 is disposed above the suction passage portion 65
and installed on an upper end of the suction passage portion
65.
[0121] The suction passage portion 65 has a cylinder member (a
third tubular member) 66, a flow passage forming member 67, and a
passage member 72. The flow passage forming member 67 is disposed
inside the cylinder member 66 in the center of the cylinder member
66. Six passage members 72 are disposed radially around the central
axis of the cylinder member 66, 60 degrees apart from each other in
the circumferential direction (see FIG. 13). The outer end portion
of the passage member 72 is welded to the cylinder member 66, and
the inner end portion of the passage member 72 is welded to the
flow passage forming member 67. Each passage member 72 slopes
downward and inward (toward the flow passage forming member 67),
and has an oval cross-sectional area (see FIG. 15). An opening 74
is formed in the outer end portion of the passage member 72. An
annular driving flow passage 76 is formed between the cylinder
member 66 and the flow passage forming member 67. Each passage
member 72 is placed across this driving flow passage 76. A suction
passage 73 communicating with the downcomer 6 through the opening
74 is formed in each passage member 72. The inner surfaces of each
passage member 72 at the inlet and the outlet of each suction
passage 73 are curved surfaces. The total flow passage
cross-sectional area of all the suction passages 73 is larger than
the cross-sectional area of a decompression chamber (an inner
region) 77 at the lower end of the nozzle portion 61. Each passage
member 72 is provided with a streamline member 75 (see FIG. 15)
having a cross-sectional area that decreases toward the upper
course to reduce the pressure loss in the driving flow passage
76.
[0122] The flow passage forming member 67 has a circular cross
section at any point in the axial direction, and includes an upper
region 68, a center region 69, and a lower region 70, each having a
different cross-sectional area in the axial direction. The upper
region 68 is cylindrical, and the center region 69 connected to a
lower end of the upper region 68 is a truncated cone. The lower
region 70 connected to a lower end of the center region 69 is an
inverted cone. The center region 69 has a cross-sectional area that
increases downward. This reduces a cross-sectional area of the
driving flow passage 76 downward between the cylinder member 66 and
the outer surface of the center region 69. The lower region 70 has
a cross-sectional area that decreases downward, and has a curved
surface 71 whose outer surface comes together in the axial
direction.
[0123] The nozzle portion 61 has an outer cylinder member (a first
tubular member) 62 and an inner cylinder member (a second tubular
member) 63 disposed in the outer cylinder member 62. The outer
cylinder member 62 is welded to a lower end of the cylinder member
66, and an upper end of the inner cylinder member 63 is welded to
the flow passage forming member 67. The outer cylinder member 62
has an outer diameter that is smaller in the lower end than in the
upper end, and slopes inward. The inner cylinder member 63 has an
outer diameter that becomes the largest in a center portion and
smaller in the upper and a lower ends. An inner end portion of the
passage member 72 is welded to the upper portion rather than the
center portion of the inner cylinder member 63. Therefore, the
inner cylinder member 63 exists between the adjacent passage
members 72 in the circumferential direction of the inner cylinder
member 63. An annular jet passage 64 is formed between the outer
cylinder member 62 and the inner cylinder member 63. The annular
jet passage 64 slopes inward, and has a flow passage
cross-sectional area that becomes smaller downward. The jet passage
64 communicates with the driving flow passage 76. The jet passage
64 is also a part of the driving flow passage. An annular ejection
outlet 20B is formed at the end of the jet passage 64. The
decompression chamber 77 is formed in the inner cylinder member 63,
and the suction passage 73 communicates with the decompression
chamber 77. The curved surface 71 of the lower region 70 of the
flow passage forming member 67 faces the decompression chamber 77.
The inner cylinder member 63 separates the driving flow passage 76
and the decompression chamber 77.
[0124] The nozzle holder 78 has a cylinder member 81, a reinforcing
streamline plate 79, and a cone member 80. The cylinder member 81
is fixed to the upper end of the cylinder member 66 of the suction
passage portion 65. The cone member 80 has a cross-sectional area
that decreases upward, and disposed in the center of the cylinder
member 81. Six reinforcing streamline plates (see FIG. 14) 79 are
radially disposed around the central axis of the cylinder member
81, 60 degrees apart from each other in the circumferential
direction, and disposed in the positions above the passage members
72 (see FIG. 13). The both ends of each reinforcing streamline
plate 79 are fixed to the cylinder member 81 and the cone member
80. A lower end portion of the cone member 80 is fitted to the
upper end portion of the flow passage forming member 67. An upper
end of the cylinder member 81 is connected to the elbow pipe
10.
[0125] It can be said that when the nozzle portion 61 and the
suction passage portion 65 are unified, the outer cylinder member
62 and the cylinder member 66 make up the first tubular member and
the inner cylinder member 63 is the second tubular member. Between
these first and second tubular members, the driving flow passage
including the jet passage 64 is formed.
[0126] The driving flow 30 pressurized by the recirculation pump 8
during the operation of the boiling water reactor flows into the
cylinder member 81 through the elbow pipe 10, and further reach the
jet passage 64 through the driving flow passage 76. This driving
flow 30 is ejected as a jet flow 31A into the bell mouth 21 from
the ejection outlet 20B located at the end of the jet passage 64.
The working of the jet flow 31A makes the suction flow 32, which is
part of the cooling water around the nozzle apparatus 12B in the
downcomer 6, to flow into the bell mouth 21 through the cooling
water suction passage 58. This suction flow 32 is introduced into
the throat 22 through the space between the bell mouth 21 and the
jet flow 31A.
[0127] Since the jet passage 64 is sloped, the jet flow 31A is
ejected diagonally toward the central axis of the throat 22 from
the ejection outlet 20B. Consequently, the working of the jet flow
31A makes the pressure in the decompression chamber 77 negative, so
that the suction flow 32A, which is part of the cooling water
descending in the downcomer 6, flows into the suction passage 73 to
reach the decompression chamber 77. This suction flow 32A further
flows into a decompression region 82 formed inside the jet flow 31A
in the bell mouth 21.
[0128] The suction flows 32 and 32A and the driving flow 30 flowing
into the bell mouth 21 are mixed in the throat 22 and discharged
from the diffuser 25 (see FIGS. 1 and 4). These flows, that is, the
cooling water 34, discharged from the diffuser 25 is supplied to
the core 2.
[0129] The jet pump 11B in the present embodiment as described
above has the following unique structures (a) to (c).
[0130] (a) The jet passage 64 in the nozzle portion 61 slopes
inward.
[0131] (b) The suction passage 73 slopes inward.
[0132] (c) A cross section of the passage member 72 forming the
suction passage 73 is oval.
[0133] Various effects obtained by the unique structures (a) to (c)
are explained in detail. First of all, various effects obtained by
the unique structure (a) are described. The jet passage 64 in the
nozzle portion 61 slopes inward. That is, the jet passage 64 slopes
inward and downward toward the central axis of the throat 22. As a
consequence, the jet flow 31A ejected from the ejection outlet 20B
is ejected downward toward the central axis of the throat 22. Such
jet flow 31A reduces the volume of the inverted cone-shaped
decompression region 82 formed inside the jet flow 31A below the
flow passage forming member 67. The reduction in the volume of the
decompression region 82 relatively increases the degree of the
pressure reduction, increasing the degree of negative pressure in
the decompression chamber 77. As a result, a flow rate Qb2 of the
suction flow 32A sucked into the bell mouth 21 through the suction
passage 73 is increased.
[0134] In addition, in the present embodiment, since the jet
passage 64 in the nozzle portion 61 slopes inward, a distance L4
between the bell mouth 21 and the end of the outer cylinder member
62 of the nozzle portion 61 can be larger. As a result, a distance
L5 between the inner surface of the throat 22 and the jet flow 31A
is increased, increasing a flow rate Qb1 of the suction flow 32
flowing into the space between the bell mouth 21 and the jet flow
31A through the cooling water suction passage 58.
[0135] An increase in the flow rate Qb1 of the suction flow 32 and
the flow rate Qb2 of the suction flow 32A increases the flow rate
of the cooling water 34 discharged from the diffuser 25. That is,
the efficiency of the jet pump 11B is further improved.
[0136] Various effects obtained by the unique structure (b) are
described. Since the suction passage 73 slopes inward, the cooling
water descending in the downcomer 6 can flow into the suction
passage 73 by only slightly changing its flow direction. This makes
the suction flow 32A to be easily sucked into the suction passage
73. In addition, since the suction passage 73 slopes inward, the
downward flow force (a flow speed of approximately 2 m/s) of the
cooling water in the downcomer 6 can be effectively used, allowing
the suction flow 32A to be easily sucked into the suction passage
73. These workings further increase the flow rate Qb2 of the
suction flow 32A, further increasing the flow rate of the cooling
water 34 as well.
[0137] Various effects obtained by the unique structure (c) are
described. Since a cross section of the passage member 72 forming
the suction passage 73 is oval, the cross-sectional area of the
suction passage 73 can be enlarged. Consequently, the pressure loss
in the suction passage 73 can be reduced and the flow rate Qb2 of
the suction flow 32A can be increased. In particular, since the
passage members 72 are disposed in such a way that their major axes
follow the axial direction of the nozzle apparatus 12B and their
minor axes follow the circumferential direction of the nozzle
apparatus 12B, the pressure loss in the suction flow passage 76 can
be reduced and the cross-sectional area of the suction passage 73
can be enlarged. In addition, such an arrangement with respect to
the major and minor axes allows the number of the passage members
72 disposed in the circumferential direction of the nozzle
apparatus 12B to be increased. Consequently, the total flow passage
cross-sectional area of all the suction passages 73 can be
enlarged. This greatly contributes to the increase in the flow rate
Qb2 of the suction flow 32A.
[0138] Besides the unique structures (a) to (c), the nozzle
apparatus 12B has some other structures that allow the yielding of
new effects. These effects are described. In order to reduce the
pressure loss in a flow passage for the driving flow 30, the nozzle
apparatus 12B adapts some ideas. A structure for reducing the
pressure loss, other than the structure in which the cross section
of the passage member 72 is oval, is explained. Each passage member
72 forms, in the upstream side, a streamline member 75 having a
cross section that decreases toward the upper course (see FIG. 15).
The formation of this streamline member 75 reduces turbulence in
the driving flow 30 flowing in the driving flow passage 76,
reducing the pressure loss in the driving flow passage 76. The
reinforcing streamline plate 79 also has a streamline shape whose
cross section decreases toward the upper course (see FIG. 14). This
structure reduces the pressure loss in the driving flow passage 76.
Furthermore, since each reinforcing streamline plate 79 is disposed
to the same position above the passage member 72 located downstream
in the circumferential direction of the nozzle apparatus 12B, the
pressure loss in the driving flow passage 76 is reduced. Since the
flow passage cross-sectional area of the jet passage 64 gradually
decreases from the upper course to the ejection outlet 20B, the
pressure loss in the jet passage 64 is also reduced. The cone
member 80 having a cross-sectional area that increases from the
upper course to the lower course, is disposed on the upper end of
the flow passage forming member 67, so that the driving flow 30
flowing in the elbow pipe 10 can be smoothly introduced to the
annular driving flow passage 76. This reduces the pressure loss in
the flow passage for the driving flow 30 in the nozzle apparatus
12B. Furthermore, in the present embodiment, the pressure loss in
the nozzle apparatus 12B can be further reduced because the nozzle
apparatus 12B forms no flow passage such as the one in the nozzle
apparatus shown in FIG. 1 of Japanese Patent Laid-open No.
2008-82752, in which the flow passage turns the driving flow at a
right angle.
[0139] The nozzle apparatus 12B employs some ideas for reducing the
pressure loss in the flow passage for the suction flow 32A. This
reduction in the pressure loss is obtained by forming curved
surfaces on the inlet and the outlet of the passage member 72 as
described above. Since the total flow passage cross-sectional area
of all the suction passages 73 is larger than the cross-sectional
area of the decompression chamber 77 at the lower end of the nozzle
portion 61, the pressure loss in the flow passage for the suction
flow 32A formed in the nozzle apparatus 12B is reduced. Since the
cross section of the passage member 72 is oval and this passage
member 72 is disposed in such a way that it slopes downward toward
the axial direction of the nozzle apparatus 12B, the opening area
of the inlet of the suction passage 73 can be enlarged. This also
decreases the pressure loss in the suction passage 73. Since the
surface of the lower region 70 of the flow passage forming member
67, facing the decompression chamber 77, is the curved surface 71,
the driving flow 32A discharged from the suction passage 73 can
smoothly change the direction downward along the curved surface 71
in the decompression chamber 77. By forming the curved surface 71
functioning in this way, the pressure loss in the flow passage for
the suction flow 32A, formed in the nozzle apparatus 12B, can be
reduced as well.
[0140] The lower region 70 of the flow passage forming member 67
protrudes below an upper end of the outlet side of the passage
member 72. Adapting such a shape allows the negative pressure in
the decompression chamber 77, which is increased by the unique
structure of (a), to effectively act on the suction passage 73, and
allows the flow rate Qb2 of the suction flow 32A flowing into the
suction passage 72 to be increased. In other words, the lower
region 70 prevents the formation of a decompression dead water
region in the decompression chamber 77 by the suction flow 32A
discharged from the suction passage 73. The lower region 70 is
disposed in the area where the decompression dead water region is
to be formed in the decompression chamber 77 when no lower region
70 is provided. For this reason, cavitation induced in the
decompression dead water region is prevented from occurring, and
the flow rate Qb2 of the suction flow 32A can be increased.
[0141] In the present embodiment, the ejection outlet 20B is
annular, making the jet flow 31A ejected from the ejection outlet
20B also annular. Thus, since a vortex generated by the jet flow
31A is evenly distributed in the circumferential direction, a
random vortex formation that causes flow-induced vibration is
prevented and consequently, the vibration of structures in the
boiling water reactor can be prevented.
[0142] Since the nozzle apparatus 12B has an annular flow passage
for the driving flow 30, the ejection outlet 20B, and the suction
passages 73 crossing the flow passage for the driving flow 30, for
introducing the suction flow 32A, the nozzle apparatus 12B can be
made compact. Therefore, by replacing a nozzle in a conventional
jet pump to the nozzle apparatus 12B, the jet pump can be quickly
and easily converted into the jet pump 11B having a higher nozzle
efficiency.
[0143] A characteristic of the jet pump having the nozzle apparatus
12B with no flow passage reduction portion in the throat is
compared with the characteristics of the conventional jet pumps in
FIG. 16. In this comparison, the conventional jet pumps are the jet
pumps having five nozzles as shown in FIG. 2 of Japanese Patent
Laid-open No. Hei 7 (1995)-119700 and the jet pumps having the
nozzle apparatus provided with a ring header and a cooling water
suction passage in the axis as shown in FIG. 1 of Japanese Patent
Laid-open No. 2008-82752. In each jet pump in Japanese Patent
Laid-open No. Hei 7 (1995)-119700 and Japanese Patent Laid-open No.
2008-82752, each ejection outlet is disposed parallel to the axis
of the jet pump, facing downward.
[0144] FIG. 16 shows a change in the jet pump efficiency to the M
ratio for the jet pump having the nozzle apparatus 12B with no flow
passage reduction portion in the throat and for the above-described
jet pumps in the conventional examples. In the jet pump having the
nozzle apparatus 12B with no flow passage reduction portion in the
throat, as described above, the efficiency increases more than the
conventional examples due to the reduction in the pressure loss in
the nozzle apparatus 12B, and the increase in the flow rates Qb1
and Qb2 of the suction flows 32 and 32A. When the M ratio is
increased for the power upgrade of the reactors, the efficiency of
the jet pump having the nozzle apparatus 12B with no flow passage
reduction portion in the throat is higher than the others as shown
in FIG. 16.
[0145] Since the jet pump 11B of the present embodiment has the
flow passage reduction portion 23 in the lower end portion of the
throat 22 in the same manner as the jet pump 11 of the embodiment
1, by the influence of this flow passage reduction portion 23, the
efficiency of the jet pump is reduced. However, this reduction in
the efficiency can be compensated for by part of the increase in
the efficiency achieved by the nozzle apparatus 12B. From the
contribution of the remaining increase in the efficiency achieved
by the nozzle apparatus 12B, the jet pump 11B, thus, can improve
the efficiency of the jet pump more than those of the conventional
examples.
[0146] The jet pump 11B of the present embodiment has the flow
passage reduction portion 23 in the lower end portion of the throat
22 so that vibration can be suppressed.
[0147] The present embodiment can increase the efficiency of the
jet pump as well as the flow rate of the cooling water 34 supplied
to the core 2. The boiling water reactor having the jet pump 11B of
the present embodiment, including the nozzle apparatus 12B, can
easily handle a power upgrade which requires a large increase in
the core flow rate. By using the nozzle apparatus 12B, a nozzle in
a jet pump in an existing boiling water reactor can be quickly
replaced. In addition, the vibration of the jet pump can be kept
low.
Embodiment 4
[0148] A jet pump according to embodiment 4, which is another
embodiment of the present invention, is described below. The jet
pump of the present embodiment is a jet pump in which a leakage
flow from the gap 27 in the slip joint 26 to the downcomer 6 is
completely eliminated from the jet pump 11 of the embodiment 1.
[0149] To completely eliminate the leakage flow from the gap 27,
the differential pressure between the inside of the slip joint 26
and the downcomer 6 should be zero. When the water head of a jet
pump is H (Pa), the density of the fluid is .rho. (kg/m.sup.3), and
its speed is v (m/s), a static pressure Pi (Pa) of the slip joint
26 is represented in Equation (3) based on the static pressure in
the downcomer 6.
Pi=H-0.5 .sigma.v.sup.2 (3)
[0150] When Pi=0, the differential pressure between the inside of
the slip joint 26 and the downcomer 6 becomes zero. The speed v is
represented in Equation (4) using a jet pump flow rate Q
(m.sup.3/s) and the inner diameter D6 of the outlet of the throat
22.
v=Q/(.pi.D6.sup.2/4) (4)
[0151] From Equation (3) and Equation (4), a value of the inner
diameter D6 that makes Pi=0 is as in Equation (5).
D6=(8.rho.Q.sup.2/.pi.H).sup.0.25 (5)
[0152] Therefore, when the inner diameter D6 is within a range of
(8.rho.Q.sup.2/.pi.H).sup.0.25.ltoreq.D6<D5, the differential
pressure between the inside of the slip joint 26 and the downcomer
6 can be reduced. A change in the static pressure in the axial
direction of the jet pump when D6=(8.rho.Q.sup.2/.pi.H).sup.0.25 in
the present embodiment is shown as the alternate long and short
dash line in FIG. 7. The differential pressure between the inside
of the slip joint 26 and the downcomer 6 becomes zero at the
position of the slip joint 26, eliminating the leakage flow from
the gap 27 in the slip joint 26.
[0153] In the present embodiment, each effect achieved in the
embodiment 1 can be obtained. The vibration of the jet pump can be
reduced more than in the embodiment 1.
Embodiment 5
[0154] A jet pump according to embodiment 5, which is another
embodiment of the present invention, is described below. A jet pump
11C of the present embodiment has a structure in which the throat
22 in the jet pump 11 of the embodiment 1 is replaced with a throat
22 having a labyrinth seal 85 on the outer surface of a thick-wall
portion 24A of the flow passage reduction portion 23 shown in FIG.
17. Other components of the jet pump 11C are the same as the jet
pump 11 of the embodiment 1.
[0155] Since the jet pump 11C is provided with the labyrinth seal
85 on the outer surface of the thick-wall portion 24A of the flow
passage reduction portion 23, the resistance of the flow passage of
the gap 27 is increased and thus a leakage flow from the inside of
the slip joint 26 to the downcomer 6 can be reduced even more than
the jet pumps in the embodiments 1 to 3. Consequently, the
vibration of the jet pump 11C can be reduced. The jet pump 11C has
the nozzle apparatus 12 so that each effect achieved by the jet
pump 11 can be obtained.
[0156] The throat 22 provided with the labyrinth seal 85 on the
outer surface of the thick-wall portion 24A of the flow passage
reduction portion 23 may be applied to the jet pumps 11A and
11B.
INDUSTRIAL APPLICABILITY
[0157] The present invention can be applied to a boiling water
reactor.
REFERENCE SIGNS LIST
[0158] 1: reactor pressure vessel, 2: core, 3: core shroud, 6:
downcomer, 7: recirculation pipe, 8: recirculation pump, 10: elbow
pipe, 11, 11A, 11B, 11C: jet pump, 12, 12A, 12B: nozzle apparatus,
13: nozzle base, 14: nozzle, 15, 17: nozzle straight-tube portion,
16, 18: nozzle narrowing portion, 19: nozzle lower end portion, 20,
20B: ejection outlet, 20A: annular ejection outlet, 21: bell mouth,
22: throat, 23: flow passage reduction portion, 25: diffuser, 26:
slip joint, 30: driving flow (driving fluid), 31, 31A: jet flow,
32, 32A: suction flow (suction fluid), 40, 61: nozzle portion, 41:
outer cylinder member, 42: inner cylinder member, 43: outer funnel
member, 44: inner funnel member, 45: annular passage, 46: nozzle
header portion, 47, 62: outer cylinder member, 48, 63: inner
cylinder member, 49: annular header portion, 50: inner cooling
water suction passage, 54: flow-adjusting plate, 57: joint portion,
64: jet passage, 65: suction passage portion, 66, 81: cylinder
member, 67: flow passage forming member, 70: lower region, 71:
curved surface, 72: passage member, 73: suction passage, 74:
opening, 77: decompression chamber, 78: nozzle holder, 79:
reinforcing streamline plate, 80: cone member.
* * * * *